A 'Big Crunch' will only be forecasted if astronomers can demonstrate that our universe has MORE than a critical density of gravitating 'stuff'.
The best estimates as of 2000, and shown in the figure above, indicate we live in an open universe with 'Omega' near 1.0. About 0.3 of this is contributed by dark matter and 0.7 by the cosmological constant which is accelerating the expansion of the universe. Oscillatory universes would 'live' in the lower right hand corner of the figure, and this is far away from where the data is leading us, the intersection of the red and blue curves, on this diagram.
I would have to rate the likelihood of finding more than the critical density as pretty remote. An oscillatory universe is not even a possibility even if the universe were to recollapse under the best of conditions anyway.
Copyright 1997 Dr. Sten Odenwald
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